Unified Communication as a Service (UCaaS) Market Size, Share & COVID-19 Impact Analysis, By Component (Telephony, Unified Messaging, Collaboration Platforms), By Delivery Model (Managed Services, and Hosted/ Cloud Services), By Organization Size (Large Enterprises, SME’s), By Vertical (BFSI, IT and Telecommunications, IT-enabled Services (ITeS), Education, Retail and Consumer Goods), and Regional Forecast, 2021 – 2028